package key

import (
	"crypto/aes"
	"crypto/ed25519"
	"crypto/rand"
	"encoding/base64"
	"strings"
	"time"
)

// ObrimKeyResponse represents the standardized utility response.
type ObrimKeyResponse struct {
	Status  bool           `json:"status"`
	Code    string         `json:"code"`
	Payload map[string]any `json:"payload"`
}

// obrimKeyAllowedSymmetricFields defines allowed symmetric configuration fields.
var obrimKeyAllowedSymmetricFields = map[string]struct{}{
	"algorithm": {},
	"key_size":  {},
}

// obrimKeyAllowedAsymmetricFields defines allowed asymmetric configuration fields.
var obrimKeyAllowedAsymmetricFields = map[string]struct{}{
	"algorithm": {},
}

// ObrimKey dispatches key generation requests and orchestrates validation, generation, and response construction.
func ObrimKey(keyType string, config map[string]any) map[string]any {
	if response := obrimKeyValidate(keyType, config); response != nil {
		return response
	}

	return obrimKeyDispatch(keyType, config)
}

// obrimKeyValidate validates common request structure and schema integrity.
func obrimKeyValidate(keyType string, config map[string]any) map[string]any {
	if strings.TrimSpace(keyType) == "" {
		return obrimKeyBuildError("FAILED_MISSING_TYPE")
	}

	if config == nil {
		return obrimKeyBuildError("FAILED_MISSING_CONFIG")
	}

	normalizedType := strings.ToLower(strings.TrimSpace(keyType))

	switch normalizedType {
	case "symmetric":
		return obrimKeyValidateSymmetricConfig(config)

	case "asymmetric":
		return obrimKeyValidateAsymmetricConfig(config)

	default:
		return obrimKeyBuildError("FAILED_UNSUPPORTED_TYPE")
	}
}

// obrimKeyDispatch routes execution to the appropriate cryptographic workflow.
func obrimKeyDispatch(keyType string, config map[string]any) map[string]any {
	switch strings.ToLower(strings.TrimSpace(keyType)) {
	case "symmetric":
		return obrimKeyGenerateSymmetric(config)

	case "asymmetric":
		return obrimKeyGenerateAsymmetric(config)

	default:
		return obrimKeyBuildError("FAILED_UNSUPPORTED_TYPE")
	}
}

// obrimKeyValidateSymmetricConfig validates symmetric configuration values.
func obrimKeyValidateSymmetricConfig(config map[string]any) map[string]any {
	for field := range config {
		if _, exists := obrimKeyAllowedSymmetricFields[field]; !exists {
			return obrimKeyBuildError("FAILED_INVALID_CONFIG_FIELD")
		}
	}

	algorithmValue, exists := config["algorithm"]
	if !exists {
		return obrimKeyBuildError("FAILED_MISSING_ALGORITHM")
	}

	algorithm, ok := algorithmValue.(string)
	if !ok {
		return obrimKeyBuildError("FAILED_INVALID_ALGORITHM")
	}

	if strings.ToLower(strings.TrimSpace(algorithm)) != "aes" {
		return obrimKeyBuildError("FAILED_UNSUPPORTED_ALGORITHM")
	}

	keySizeValue, exists := config["key_size"]
	if !exists {
		return obrimKeyBuildError("FAILED_MISSING_KEY_SIZE")
	}

	keySize, ok := obrimKeyConvertInt(keySizeValue)
	if !ok {
		return obrimKeyBuildError("FAILED_INVALID_KEY_SIZE")
	}

	switch keySize {
	case 128, 192, 256:
		return nil
	default:
		return obrimKeyBuildError("FAILED_UNSUPPORTED_KEY_SIZE")
	}
}

// obrimKeyValidateAsymmetricConfig validates asymmetric configuration values.
func obrimKeyValidateAsymmetricConfig(config map[string]any) map[string]any {
	for field := range config {
		if _, exists := obrimKeyAllowedAsymmetricFields[field]; !exists {
			return obrimKeyBuildError("FAILED_INVALID_CONFIG_FIELD")
		}
	}

	algorithmValue, exists := config["algorithm"]
	if !exists {
		return obrimKeyBuildError("FAILED_MISSING_ALGORITHM")
	}

	algorithm, ok := algorithmValue.(string)
	if !ok {
		return obrimKeyBuildError("FAILED_INVALID_ALGORITHM")
	}

	if strings.ToLower(strings.TrimSpace(algorithm)) != "ecc" {
		return obrimKeyBuildError("FAILED_UNSUPPORTED_ALGORITHM")
	}

	return nil
}

// obrimKeyGenerateSymmetric generates symmetric key material.
func obrimKeyGenerateSymmetric(config map[string]any) map[string]any {
	normalizedConfig := obrimKeyNormalizeSymmetricConfig(config)

	payload, errorCode := obrimKeyGenerateAES(normalizedConfig)
	if errorCode != "" {
		return obrimKeyBuildError(errorCode)
	}

	return obrimKeyBuildPayload(payload)
}

// obrimKeyGenerateAES generates AES key material.
func obrimKeyGenerateAES(config map[string]any) (map[string]any, string) {
	keySize := config["key_size"].(int)

	// obrimKeyMaterial stores generated AES key bytes.
	keyMaterial := make([]byte, keySize/8)

	if _, err := rand.Read(keyMaterial); err != nil {
		return nil, "FAILED_KEY_GENERATION"
	}

	if _, err := aes.NewCipher(keyMaterial); err != nil {
		return nil, "FAILED_KEY_GENERATION"
	}

	return map[string]any{
		"type":         "symmetric",
		"algorithm":    "aes",
		"key_size":     keySize,
		"key_material": base64.StdEncoding.EncodeToString(keyMaterial),
		"generated_at": time.Now().UTC().Format(time.RFC3339),
	}, ""
}

// obrimKeyNormalizeSymmetricConfig normalizes symmetric configuration values.
func obrimKeyNormalizeSymmetricConfig(config map[string]any) map[string]any {
	keySize, _ := obrimKeyConvertInt(config["key_size"])

	return map[string]any{
		"algorithm": strings.ToLower(strings.TrimSpace(config["algorithm"].(string))),
		"key_size":  keySize,
	}
}

// obrimKeyGenerateAsymmetric generates asymmetric key material.
func obrimKeyGenerateAsymmetric(config map[string]any) map[string]any {
	normalizedConfig := obrimKeyNormalizeAsymmetricConfig(config)

	payload, errorCode := obrimKeyGenerateECC(normalizedConfig)
	if errorCode != "" {
		return obrimKeyBuildError(errorCode)
	}

	return obrimKeyBuildPayload(payload)
}

// obrimKeyGenerateECC generates ECC key pair material.
func obrimKeyGenerateECC(config map[string]any) (map[string]any, string) {
	publicKey, privateKey, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		return nil, "FAILED_KEY_GENERATION"
	}

	return map[string]any{
		"type":         "asymmetric",
		"algorithm":    "ecc",
		"curve":        "eddsa",
		"public_key":   base64.StdEncoding.EncodeToString(publicKey),
		"private_key":  base64.StdEncoding.EncodeToString(privateKey),
		"generated_at": time.Now().UTC().Format(time.RFC3339),
	}, ""
}

// obrimKeyNormalizeAsymmetricConfig normalizes asymmetric configuration values.
func obrimKeyNormalizeAsymmetricConfig(config map[string]any) map[string]any {
	return map[string]any{
		"algorithm": strings.ToLower(strings.TrimSpace(config["algorithm"].(string))),
	}
}

// obrimKeyBuildPayload constructs standardized success payloads.
func obrimKeyBuildPayload(payload map[string]any) map[string]any {
	return map[string]any{
		"status":  true,
		"code":    "SUCCESS_KEY_GENERATED",
		"payload": payload,
	}
}

// obrimKeyBuildError constructs standardized error responses.
func obrimKeyBuildError(code string) map[string]any {
	return map[string]any{
		"status":  false,
		"code":    code,
		"payload": nil,
	}
}

// obrimKeyConvertInt converts supported numeric values to int.
func obrimKeyConvertInt(value any) (int, bool) {
	switch converted := value.(type) {
	case int:
		return converted, true
	case int8:
		return int(converted), true
	case int16:
		return int(converted), true
	case int32:
		return int(converted), true
	case int64:
		return int(converted), true
	case uint:
		return int(converted), true
	case uint8:
		return int(converted), true
	case uint16:
		return int(converted), true
	case uint32:
		return int(converted), true
	case uint64:
		return int(converted), true
	case float32:
		if float32(int(converted)) == converted {
			return int(converted), true
		}
	case float64:
		if float64(int(converted)) == converted {
			return int(converted), true
		}
	}

	return 0, false
}